This invention is directed to gasifiers and more particularly to a novel replaceable insert for a gasifier floor, and a novel refractory hanging brick for protecting an edge portion of the gasifier floor, especially the replaceable insert for the gasifier floor.
Gasifiers are generally used for processing carbonaceous fuels, including coal, petroleum coke, gas and/or oil, to produce gaseous mixtures of hydrogen and carbon monoxide, such as coal gas, synthesis gas, reducing gas and fuel gas.
Partial oxidation gasifiers of the type shown in U.S. Pat. No. 2,809,104 and U.S. Pat. No. 5,484,554 include a high temperature reaction chamber surrounded by one or more layers of insulating and refractory material, such as fire clay brick, also referred to as refractory brick or refractory lining, and encased by an outer steel shell or vessel.
A feed injector such as shown in U.S. Pat. No. 4,443,230 and U.S. Pat. No. 4,491,456, can be used with gasifiers of the type shown in the previously referred to patents to introduce pumpable slurries of carbonaceous fuel, such as a coal-water slurry, downwardly into a reaction chamber of the gasifier along with oxygen containing gases for partial oxidation.
During operation of the gasifier typical reaction chamber temperatures can range from approximately 2200° F. to 3000° F. Operating pressures can range from 10 to 200 atmospheres. Thus, the coal-water slurry that passes through the feed injector nozzle normally self-ignites at the operating temperatures of the gasifier.
As the coal-water slurry reacts within the gasifier, one of the reaction products is gaseous hydrogen sulfide, a well known corrosive agent. Molten or liquid slag is also formed during the gasification process, as a by-product of the reaction between the coal-water slurry and the oxygen containing gas. Slag is also a well known corrosive agent and gradually flows downwardly along the inside walls of the gasifier to a water bath of the type shown in U.S. Pat. No. 5,464,592. The water bath cools the syngas exiting from the reaction chamber and also cools any slag that drops into the water bath.
Before the downflowing molten slag reaches the water bath, it flows through a throat section at a floor portion of the gasifier and closely past a quench ring and dip tube that leads to the water bath. The quench ring, which is formed of a chrome nickel iron alloy or nickel based alloy such as Incoloy®, is arranged to spray or inject water as a coolant against the inner surface of the dip tube. However some portions of the quench ring are in the flow path of the downflowing molten slag, and the quench ring can thus be contacted by molten slag. The portions of the quench ring that are contacted by slag may experience temperatures of approximately 1800° F. to 2800° F. The quench ring thus is vulnerable to thermal damage and thermal chemical degradation. Slag may also solidify on the quench ring and accumulate to form a plug that can restrict or eventually close the throat opening. Furthermore any slag accumulation on the quench ring will reduce the ability of the quench ring to perform its cooling function.
In one known gasifier the metal floor portion of the reaction chamber is in the form of a frustum of an upside down conical shell. The metal floor is usually made of the same pressure vessel metallurgy as the gasifier shell or vessel. The throat structure for the gasifier is provided at a central opening in the gasifier floor.
The metal gasifier floor supports refractory material such as ceramic brick, that covers the metal floor, and also supports the refractory material that covers the inner surface of the gasifier vessel above the gasifier floor. The gasifier floor can also support an underlying quench ring and dip tube of the type shown in U.S. Pat. No. 5,464,592.
A peripheral edge of the gasifier floor at the throat section, also know as a leading edge, is usually exposed to the harsh conditions of high temperature, high velocity syngas (which may have entrained particles of erosive ash, depending on the nature of the feedstock) and slag. The metal floor suffers wastage in a radial direction (from the center axis of the gasifier), beginning at the leading edge and progressing radially outward until the harsh conditions created by the hot syngas are in equilibrium with the cooling effects of the underlying quench ring. The metal wasting action thus progresses radially outward from a center axis of the gasifier until it reaches an “equilibrium” point or “equilibrium” radius.
The equilibrium radius is occasionally far enough from the center axis of the gasifier and the leading edge of the floor such that there is a risk that the floor can no longer sustain the overlying refractory. If refractory support is in jeopardy, the gasifier may require premature shut down for reconstructive work on the floor and replacement of the throat refractory, a very time intensive and laborious procedure.
Another problem at the throat section of the gasifier is that the upper, curved surface of the quench ring is exposed to full radiant heat from the reaction chamber of the gasifier, and the corrosive/erosive effects of the high velocity, high temperature syngas which can include ash and slag. Such harsh conditions can also lead to wastage problems of the quench ring which, if severe enough, can force termination of gasification operations for necessary repair work. This problem is exacerbated if the overlying floor has wasted away significantly, exposing more of the quench ring to the hot gas and slag.
It is thus desirable to provide a replaceable floor insert device which enables the gasifier floor to be repaired relatively easily. It is also desirable to provide a protective refractory device for the leading edge of the floor that minimizes the rate of metallurgy wastage of the floor and any underlying quench ring.